Is the work of a gold distributor who sells crafted gold and receives the manufacturing cost in cash, while delaying the receipt or payment of the value of the gold itself from some merchants, considered usury (riba)? And what is advised to avoid that if it is unlawful?

It is forbidden to sell gold for gold with an added manufacturing fee, because this is riba al-fadl (usury of excess), as there must be equality between manufactured gold and unmanufactured gold. It is also forbidden to sell gold for gold with delayed possession or payment, because this combines riba al-fadl and riba al-nasi’ah (usury of delay).

The correct method is to sell old gold for money, then buy new gold with the same money, or to give the old gold to the jeweler for manufacturing in exchange for a cash fee.